der_wille_zur_macht
Team RC
Depends on a lot of factors. I'd estimate between 80 - 100 LEDs total, so maybe 36 on each module.
Depends on what color you like. If you're building three modules, you might want to get a bunch of each color and play with the numbers to get the exact look you want. Most people seem to like 50/50. It's about equivalent to a 10kk MH with strong actinic supplementation.
At 10 - 15" up and a moderately deep tank, I'd probably go with wide optics - 60-80 degrees.
Sadly it's hard to make the conversions you're trying to make. There is no real way to convert from a wavelength of light to a kelvin color. Wavelength is a pure physical measurement - when a blue LED is labeled as 450nm, that means it peaks strongly at that exact wavelength, and has virtually no output elsewhere. Meanwhile, the kelvin scale is used to approximately describe "whitish" light, i.e. light from full spectrum sources that cover a very large wavelength. But even at that task it fails pretty spectacularly. Above I mentioned a very rough approximation, you can use that as a guide.
Another consideration is that the published specs (both wavelength for the blues and kelvin for the cool whites) are very rough guides in the first place. The LEDs are also labeled with a color bin. For colored LEDs like the royal blue, the color bin indicates the donminant wavelength. For cool white LEDs, the color bin indicates a polygon on a slice of the the CIE 1931 XYZ color space, which is basically a 2-d way to approximate the color of full spectrum light. Meanwhile, the kelvin scale is one dimensional (linear). This adds yet another important dimension to the consideration, because two color bins on that CIE 1931 graph might be assigned the same "kelvin" color, but to your eye, they may look very different.
That said, in general:
- 60/40 cool white/royal blue will look like a plain 10kk MH lamp.
- 50/50 cool white/royal blue will look like a 10kk MH with actinic supplementation
- 40/60 cool white/royal blue will look like a 15kk MH with actinic supplementation
And I'll repeat my suggestion above - people building smaller fixtures should get two or three extra of each color, then play with the counts to get the color they want. People making large fixtures should probably experiment with sub-units or smaller test fixtures first to get the balance they want.
In contrast, many people buy dimmable drivers with the intention of dimming one color or the other to fine-tune the look of the finished product. That's fine, but it's important to note that doing so also impacts the overall intensity of the fixture. An innocent twist of a knob on a dimmable driver can impact intensity by a very large margin, so it's something to consider. IMHO a "best practice" approach would be to build the fixtures with the balance you want in the first place, then use dimming to adjust afterwards if you want to tweak it, with considerations for overall intensity.
